This application claims the benefit of Korean Application Nos. 2000-74762 and 2001-13235 filed on Dec. 8, 2000 and Mar. 14, 2001, respectively, in the Korean Industrial Property Office, the disclosures of which are incorporated herein by reference.
1. Field
The present invention relates to a cathode ray tube, and more particularly, to a shrinkage band and a cathode ray tube comprising the same.
2. Background
A cathode ray tube (CRT) is a display device in which an electron beam emitted from an electron gun excites phosphors on a phosphor screen such that the phosphors emit light, thereby creating various images. A three-ray electron beam is deflected by a deflection yoke to provide a raster scan and is separated into red (R), green (G), and blue (B) phosphors by a shadow mask, which functions as a color selection apparatus, to create precise colors.
The three-ray electron beam emitted from the electron gun illuminates designated phosphors with an accurate raster scan by way of a deflected magnetic field which corresponds precisely to apertures of the shadow mask. However, the earth""s magnetic field affects the movement of electrons within the CRT. That is, the earth""s magnetic field affects convergence characteristics of the electron beams (the degree to which the three-ray electron beam is focused to a single point), raster position, and purity characteristics.
The earth""s magnetic field includes both horizontal and vertical components, i.e., horizontal and vertical to the earth""s surface, and the intensity of the earth""s magnetic field varies depending on the geographical location and positioning of the CRT. The horizontal component of the earth""s magnetic field in particular affects the path of the electron beam raster and convergence. It is therefore very advantageous to block the horizontal component of the earth""s magnetic field.
Heretofore, an inner shield for blocking the earth""s magnetic field has been mounted in the CRT. The inner shield reduces changes in the landing of the electron beams caused by the earth""s magnetic field by approximately 50%. However, there has been little improvement in the area of effectively blocking the affect of the earth""s magnetic field, and particularly the horizontal component of the earth""s magnetic field on the electron beams directed toward the phosphor screen once they has passed the inner shield.
Referring to FIG. 1, a bulb defining the CRT includes a glass face panel, a funnel, and a neck, which are fused to form the bulb. Also, a shrinkage band 5 applying a predetermined tension is mounted on the bulb 3 around an outer circumference of the face panel 1. The shrinkage band 5 acts to prevent the scattering of glass if the bulb 3 implodes as a result of external impact.
With regard to the mounting of the shrinkage band 5, tape (not shown) is first applied to the area on the bulb 3 where the shrinkage band 5 will be positioned. Next, the shrinkage band 5 is heated to between 500 and 600xc2x0 C. to expand the same. In this state, the shrinkage band 5 is placed around the bulb 3 and is then cooled, which causes the shrinkage band 5 to shrink. Accordingly, the shrinkage band 5 is mounted on the bulb 3, applying a predetermined tension thereto.
The shrinkage band 5 is typically made of low carbon steel, which is inexpensive and has a low permeability. However, besides its use to provide support to the bulb 3, the shrinkage band 5 has not been applied to improve the magnetic field characteristics of the CRT.
In one aspect of the present invention, a shrinkage band for a cathode ray tube (CRT) includes a pair of spaced apart parallel first sides, a pair of spaced apart parallel second sides perpendicular to the first sides, the second sides being longer than the first sides, and corner portions connecting the first and second sides such that the corner portions are provided at four corners of the shrinkage band, wherein the shrinkage band is configured to go around an outer circumference of a CRT face panel skirt to apply tension to the face panel, and wherein the first sides, and the second sides, a different magnetic permeability.
In another aspect of the present invention, a cathode ray tub includes a bulb including a face panel having a screen portion and a skirt, a neck, and a funnel between the face panel and the neck, the face panel, the funnel, and the neck being integrally formed, a phosphor screen on an inside surface of the screen portion, an electron gun configured to emit a three-ray electron beam toward the phosphor screen, a deflection element mounted to an outer circumference of the funnel and configured to generate a deflecting magnetic field to deflect the electron beam, an inner shield mounted within the bulb such that the inner shield surrounds a path of the electron beam, the inner shield being configured to reduce the influence of the earth""s magnetic field, and a shrinkage band mounted around an outer circumference of the skirt to apply tension to the face panel, the shrinkage band having a pair of spaced apart parallel first sides, a pair of spaced apart parallel second sides perpendicular to the first sides, the second sides being longer than the first sides, and corner portions connecting the first and second sides such that the corner portions are provided at four corners of the shrinkage band, wherein the first sides, the second sides, and the corner portions comprise two materials each having a different permeability.
It is understood that other aspects of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein is shown and described only exemplary embodiments of the invention, simply by way of illustration. As will be realized, the invention is capable of other and different embodiments, and its several details are capable of modifications in various respects, all without departing from the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.